Efficacy of certain biopesticides against whitefly, Bemesia tabaci (Gennadius) on okra and its correlation with abiotic factors

Abstract

A field experiment was carried out at the Assam Agricultural University, Jorhat, Assam, India during 2018-2019 to evaluate the efficacy of different biopesticides against whitefly, Bemesia tabaci (Gennadius) on okra. The treatments viz., neem oil @ 5%, karanj oil @ 5%, Melia azedarach leaf extract @ 5%, garlic extract @5%, chilli fruit extract @5%, Beauveria bassiana @ 5%, Lecanicillium lecanii @ 5%, deltamethrin @ 10 g a.i./ha were applied at 15 days interval starting from seedling stage when whitefly infestation started. Results revealed that overall best performance of insecticides against whitefly recorded in deltamethrin treated plots with lowest mean population followed by neem oil, Verticillim lecanii. And observations for whiteflies were recorded at a weekly interval from three leaves per plant, starting from 14th Standard Meteorological Week (SMW). The maximum population of whiteflies (14.91 whiteflies/3
leaves) was observed during the 18th SMW. While the minimum population of whiteflies (3.04 whiteflies/3 leaves) was observed during 31st SMW. Whitefly population was significantly and negatively correlated with maximum temperature and minimum temperature and positively correlated with the bright sunshine hours and the correlation of whiteflies with all other weather parameters was negative and non-significant.